Victorian-era photographs...of the moon? In 3-D?!
I have long had a great interest in the history of photography and consider myself an expert in that field, so volunteering in the Museum’s photographic history collection is perfect for me. The collection contains many truly great and priceless items from the history of photography and it really excites me to look at them and hold them. Two objects from the Victorian era are particularly interesting to me. Why? Because taking a 3-D photograph of the Moon should not be possible—at least not to Victorian photographers—but they figured out how to do it!
The two photographs of the last quarter Moon used for the stereo card shown here were taken by noted pioneer astrophotographer Henry Draper (1837-1882). His father, John Draper, was the first to photograph the Moon in 1840. Henry took a series of detailed photographs of the Moon in 1863 using a reflecting telescope. It was these photographs that were used to make 3-D cards of the Moon including the one shown. They are important because they are the very first 3-D images of an object in space.
A stereoscopic photograph requires two slightly different views seen through a special viewer. Using binocular vision, our brain takes in the two images and translates them into a perceived three-dimensional effect. The average separation between an adult's eyes is 3 inches, and we can see objects up to 300 feet away in 3-D. To achieve a 3-D view of distant astronomical objects, the separation between our eyes needs to be much greater. To see the moon in 3-D the distance between our eyes would need to be about 60,000 miles, or more than seven times the diameter of the Earth!
Thus taking a 3-D photograph of the moon from the Earth looks impossible, but Victorian-era photographers proved that with patience it could be done. The Moon appears to wobble from side to side in its orbit around the Earth. This means that if two photographs of the same phases are taken three or four months apart they are able to give a pronounced stereoscopic effect when placed side by side in a 3-D viewer.
This interesting technique only works for the Moon, but is not without difficulties. The two photographs have to be taken at exactly the same phase of the Moon potentially spread in time over months and using the same camera or telescope. Other possible problems include bad weather, the Moon below the horizon, or the Sun up when the correct phase is reached. These factors could considerably increase the time between two suitable images. However, Henry Draper overcame all these problems to make several 3-D photographs of the Moon. The Photographic History Collection also includes three additional stereoscopic cards made from photographs by Draper, two cards of the Moon at first quarter and one card of the full Moon.
Anthony Brooks is a volunteer in the Photographic History Collection at the National Museum of American History. He retired in 2005 from a 30 years plus career as a nuclear scientist.